The example projects only show drools, xPath, and cron as language attribute in conditionExpressions. I tried the above and it didn't work. IIRC it failed in KnowledgeBuilder.
Then I tried
<conditionExpression xsi:type="tFormalExpression" language="http://www.jboss.org/drools/rule">PIvars(applicationReady == true);</conditionExpression>
The Gateway ignored it.
This ugly one does work but if there is a clean way that works I'd like to know.
<conditionExpression xsi:type="tFormalExpression">
org.drools.runtime.process.WorkflowProcessInstance process = (org.drools.runtime.process.WorkflowProcessInstance)kcontext.getProcessInstance();
edu.berkeley.ouae.workflow.dto.FreshmanReadPIvars vars = process.getVariable("vars");
return vars.isApplicationReady() == false;</conditionExpression>